The invention relates to a Diston engine having a hypocycloidal piston stroke transmission with a Watt's guide, particularly with pistons in opposed cylinders. An engine of this type is known from German Patent Document DE-A 41 08 311.
It is known that the connecting center point of a Watt's guide describes a precise straight-line path only by means of connecting control arms of an infinite length, whereas, in the case of real control arms of particularly short lengths, as, for example, on a piston engine, the connecting center point, along the overall stroke of the oscillating connecting rod, describes a path curve which is curved several times with respect to the fictitious or ideal straight guiding line and changes this straight guiding line.
The essay "Calculating Watt's Straight-Line Transmissions" in Volume 1/1980 of the journal of the German Democratic Republic with the title "Maschinenbautechnik" ("Mechanical Engineering Technology") shows particularly by means of a nomogram illustrated in Page 27 possibilities of adapting such a path curve in its deviations and courses according to the application of the Watt's guide as a function of its transmission parameters to the desired quality, of straight line guiding. It is the main goal to minimize the transverse deviations of the path curve of the connecting center point from the fictitious or ideal straight guiding line and to render the deviations uniform.
As it was found, such a design of a Watt's guide used in a hypocycloidal piston stroke transmission results in transverse displacements of such different dimensions of the stroke eccentric connected with respect to the drive with a piston push rod that any piston guiding is affected negatively.
It is an object of the invention to improve, in the case of a piston engine of the above-mentioned type having a hypocycloidal piston stroke transmission with a Watt's guide, the moving course of stroke eccentric transversely to its moving path such that, with respect to the amount, transverse displacements of the stroke eccentric which are approximately identical are achieved and thus also, by way of the piston stroke, of the piston connected with it.
This object is achieved by providing a piston engine having a hypocycloidal piston stroke transmission with a Watt's guide, particularly with pistons in opposed cylinders. A stroke eccentric is connected, with respect to the drive, with a push rod of a piston guided in a cylinder. A guide eccentric is guided orthogonally to the stroke eccentric path or piston path by means of the Watt's guide. The stroke eccentric and guide eccentric are arranged on the crank pin of a crankshaft. The guide eccentric is non-rotatably connected with the stroke eccentric and is rotatably disposed in a Watt's connecting rod controlled by way of control arms swivellably disposed on the motor housing. Parameters of the Watt's guide are selected such that a path course is forced upon the guide eccentric, which oscillates orthogonally with respect to the path of the stroke eccentric or piston, along each moving range close to its respective reversal point by means of the Watt's connecting rod which progressively deviates from the ideal orthogonal guide path such that, during each passage of the stroke eccentric through the intersection point of the guide path with the path of the stroke eccentric or piston path the guide eccentric has a maximal deviation .increment.q.sub.F from the ideal guide path.
By means of the invention, the transverse deviations of the stroke eccentric which is connected with the piston push rod with respect to the drive, which differ considerably particularly with respect to the amounts, are advantageously rendered uniform to an advantageously selectable extent of transverse deviation which significantly reduces the influence on a transverse displacement/slant of the piston in the respective cylinder. This is achieved by means of a course of the path of the connecting center point which deviates in a targeted manner and thus of the guide eccentric center point with a largest possible deviation in the respective reversal point of the connecting rod only by means of a coordination of the parameters of the Watt's guide according to the invention which differs from the known state of the art.
In a further development of the invention, the length of the control arms was recognized as the advantageously dominant parameter of the Watt's guide which is obtained in the case of the zero position of the Watt's connecting rod with the center point M.sub.FE of the guide eccentric situated in the intersection point of the guide path and the stroke eccentric or piston path and with control arms extending essentially in parallel to the stroke eccentric path, specifically as follows: EQU L.sub.control arm =h+0.17765.times.s.times.(4.times.h/s).sup.-1.0335
wherein s=piston stroke and h=distance of a housing-side control arm point of rotation from the guide path, and the following is the definition range: 3.5.ltoreq.(4.times.h/s).ltoreq.15.
The formula according to the invention for the length of the control arms of the Watt's connecting rod advantageously permits by means of only two definable construction data of a piston engine of the above-mentioned type a design of the Watt's guide according to the invention when used in a hypocycloidal piston stroke transmission. A characteristic of the design according to the invention is a path course which is as straight as possible with transverse deviations of a low amount of the stroke eccentric connected with respect to the drive with the piston push rod which are rendered uniform, achieved by extreme transverse deviations from the ideal or fictitious guide path in close ranges of its reversal points of the guide eccentric non-rotatably connected with the stroke eccentric about the crank pin of the crankshaft by means of the Watt's connecting rod (FIG. 3).
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.